4-(Dimethyl)amino-1,3,4,5-tetrahydrobenz[cd]indole was prepared by Stoll and Petrzilka, Helv. Chim. Acta., 35, 148 (1952). The compound was used as an intermediate in a Hofmann degradation. 4-Amino-1,3,4,5-tetrahydrobenz[cd]indole is disclosed in J. Pharm. Exptl. Therap., 128, 358 (1960) as a 5-hydroxytryptophane antagonist.